Position detector with a minimum magnetic flux density position shifted from a center of a gap

ABSTRACT

A position detector includes a magnet disposed between first ends of first and second magnetic flux transmission parts and a magnet disposed between second ends of the first and second magnetic flux transmission parts. The position detector also includes a Hall IC that is positioned within a gap and moves relative to a rotating body. The Hall IC detects a density of the magnetic flux from the first and second magnetic flux transmission parts and outputs a signal according to the density of the magnetic flux passing therethrough in order to detect a position of a detection object. A minimum magnetic flux density position within the gap may be shifted to a position having the highest detection accuracy such that the position detection accuracy of the detection object is improved.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.14/142,168, filed Dec. 27, 2013, which claims the benefit of priority ofJapanese Patent Application No. 2012-286098 filed on Dec. 27, 2012, thedisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a position detector fordetecting a position of a detection object.

BACKGROUND

Generally, a magnetic-type position detector detects a change in theposition of a detection object relative to a reference part. Themagnetic-type position detector may utilize a magnetic flux generatorsuch as a magnet. For example, a position detector disclosed in a patentdocument 1 (i.e., Japanese Patent Laid-Open No. JP-A-H08-292004) isconfigured to form a closed magnetic circuit having two magnets and twomagnetic flux transmission parts that are disposed on a reference part.In such structure, the two magnets are respectively bound by the ends ofthe two mutually-facing magnetic flux transmission parts. A flow ofspill magnetic fluxes from one transmission part to the other occurswithin a gap between the respective ends of the two magnetic fluxtransmission parts. A magnetic flux density detector is configured tomove together with the detection object within the gap between the twomagnetic flux transmission parts and to output a detection signalaccording to the magnetic flux passing therethrough. In such manner, theposition detector detects the position of the detection object relativeto the reference part based on an output signal that is output from themagnetic flux detector.

In the position detector of a patent document 1, two magnets of the samemagnet type having the same volume are disposed at both ends of each ofthe two magnetic flux transmission parts, with the polarity of the twomagnets arranged in opposite directions to each other. Therefore, at thecenter of the gap between the two magnetic flux transmission parts, thedirection of the magnetic flux is reversed. In other words, a centerposition of a movable range of the detection object and the magneticflux density detector is a position where an absolute value of themagnetic flux density decreases to a minimum value (hereinafter “minimumMF density position”).

Generally, it is observed that the minimum magnetic flux densityposition within the movable range of the detector providestemperature-resistance against the effects of temperature changes due tothe detector environment. That is, at such a position, the magneticpower of the magnets changes minimally even when the temperature of thedetector environment changes (i.e., a temperature coefficient of themagnetic flux generator is low at such position). In other words, at theminimum magnetic flux density position, a position detection accuracy ofthe detector is higher than at other positions. Such a characteristic ofthe detector in the patent document 1 is perceived as having lowerposition detection accuracy at positions other than the center positionof the detector movable range. That is, at both ends of the detectormovable range (i.e., the gap), for example, the position detectionaccuracy of the detector may be low. Such a characteristic of thedetector may also be interpreted as having a high position detectionaccuracy that occurs only at a center position of the detector movablerange, which may be undesirable in some applications. That is, forexample, when high position detection accuracy is required at both endsof the detector movable range, a position detector having low positiondetection accuracy at the ends of the detector movable range may not besuitable for certain applications.

SUMMARY

It is an object of the present disclosure to provide a position detectorhaving improved position detection accuracy and temperature resistance.

In an aspect of the present disclosure, the position detector detects aposition of a detection object that moves relative to a reference part.The position detector includes a first magnetic flux transmission partdisposed on one of the detection object or the reference part, the firstmagnetic flux transmission part having a first end and a second end anda second magnetic flux transmission part disposed to define a gapbetween the first magnetic flux transmission part and the secondmagnetic flux transmission part, the second magnetic flux transmissionpart having a first end and a second end. A first magnetic fluxgenerator is disposed at a position between the first end of the firstmagnetic flux transmission part and the first end of the second magneticflux transmission part and a second magnetic flux generator is disposedat a position between the second end of the first magnetic fluxtransmission part and the second end of the second magnetic fluxtransmission part. A magnetic flux density detector (i) is disposed onan other of the detection object or the reference part to be movablewithin the gap relative to the one of the detection object or thereference part and (ii) outputs a signal according to a density of amagnetic flux passing through the magnetic flux density detector. Aminimum magnetic flux density position of the magnetic flux densitydetector within the gap, where an absolute value of the density of themagnetic flux passing through the magnetic flux density detectordecreases to a minimum, is set to a position that is shifted away from acenter of the gap by a predetermined distance toward one of the firstmagnetic flux generator or the second magnetic flux generator.

Further, the first magnetic flux generator is a permanent magnet, thesecond magnetic flux generator is a permanent magnet, and at least oneof a magnet volume, a magnet type, a magnet material composition, or amagnetization adjustment method of the first magnetic flux generator isdifferent from the second magnetic flux generator.

Moreover, the first magnetic flux generator has at least one permanentmagnet, the second magnetic flux generator has a different number ofpermanent magnets than the first magnetic flux generator, and identicalpermanent magnets are used for the at least one permanent magnet of thefirst magnetic flux generator and the different number of permanentmagnets of the second magnetic flux generator.

In addition, a third magnetic flux transmission part made of anidentical material as the first magnetic flux transmission part and thesecond magnetic flux transmission part. The third magnetic fluxtransmission part replaces one of the first magnetic flux generator orthe second magnetic flux generator.

Additionally, the thickness of at least one of the first magnetic fluxtransmission part or the second magnetic flux transmission part changesin a direction from the first magnetic flux generator to the secondmagnetic flux generator.

Furthermore, the detection object rotates relative to the referencepart, and the first magnetic flux transmission part and the secondmagnetic flux transmission part have a curved shape that is concentricto a center of rotation of the detection object.

Even further, the detection object moves linearly relative to thereference part, and the first magnetic flux transmission part and thesecond magnetic flux transmission part have a straight shape thatextends along a path of relative movement of the detection object.

Moreover, in another aspect of the present disclosure, the positiondetector detects a position of a detection object that moves relative toa reference part. The position detector includes a first magnetic fluxtransmission part disposed on one of the detection object or thereference part, the first magnetic flux transmission part having a firstend and a second end, and a second magnetic flux transmission partdisposed to define a gap between the first magnetic flux transmissionpart and the second magnetic flux transmission part, the second magneticflux transmission part having a first end and a second end. A magneticflux generator disposed at a position between the first end of the firstmagnetic flux transmission part and the first end of the second magneticflux transmission part. A magnetic flux density detector (i) is disposedon an other of the detection object or the reference part to be movablerelative to the one of the detection object or the reference part withinthe gap and (ii) outputs a signal according to a density of a magneticflux passing therethrough. A minimum magnetic flux density position ofthe magnetic flux density detector within the gap, where an absolutevalue of the density of the magnetic flux passing through the magneticflux density detector decreases to a minimum, is set to a position thatis shifted away from a center of the gap by a predetermined distanceaway from the magnetic flux generator.

In other words, the position detector detects a relative move positionof a detection object, which is a position after a relative move of thedetection object relative to a reference part, the detector includes: afirst magnetic flux transmission part, a second magnetic fluxtransmission part, a first magnetic flux generator, a second magneticflux generator, and a magnetic flux density detector.

The first magnetic flux transmission part is disposed on one of thedetection object and the reference part. The second magnetic fluxtransmission part is disposed on one of the detection object or thereference part, so that a gap is formed at a position between the firstand second magnetic flux transmission parts.

In other words, the first magnetic flux generator is disposed at aposition between a first end of the first magnetic flux transmissionpart and first end of the second magnetic flux transmission part.Thereby, the magnetic flux generated by the first magnetic fluxgenerator is transmitted from the first end of the first and secondmagnetic flux transmission parts to a second end of first and secondmagnetic flux transmission parts.

The second magnetic flux generator is disposed at a position between thesecond end of the first magnetic flux transmission part and the secondend of the second magnetic flux transmission part. Thereby, the magneticflux generated by the second magnetic flux generator is transmitted fromthe second end of the first and second magnetic flux transmission partsto the first end of first and second magnetic flux transmission parts.

The magnetic flux density detector is disposed on the one of thedetection object or the reference part so that the detector is movablerelative to the other of the detection object or the reference part inthe gap between the first and second magnetic flux transmission parts.The magnetic flux density detector outputs a signal according to adensity of the magnetic flux passing through the detector. In such astructure, the magnetic flux passing through the magnetic flux densitydetector is, mainly, a spill magnetic flux, which flows through the gapbetween the first and second magnetic flux transmission parts from oneof the two transmission parts to the other (i.e., the magnetic fluxflowing either from the first part to the second part or from the secondpart to the first part).

By devising the above-mentioned configuration, the position detector isenabled to detect a position of the detection object relative to thereference part based on the signal outputted by the magnetic fluxdensity detector.

In the present disclosure, a minimum magnetic flux (MF) densityposition, where an absolute value of a magnetic flux density detectedand output by the magnetic flux density detector decreases to a minimum,is set at a position that is shifted away from a center of the movablerange of the detector by a predetermined distance to the left or to theright, that is, toward the first or second magnetic flux generator alonga range of relative movement of the detector. That is, in other words,the minimum MF density position having the minimum absolute magneticflux density value is set at a position that is shifted position awayfrom the center position of the movable range of the detection object.Therefore, the minimum MF density position may be moved and set at aposition where the highest detection accuracy is required for theaccurate position detection of the detection object.

Generally, it is observed that the minimum MF density position withinthe movable range of the detector provides a good temperature-proofingcharacter for the temperature change of the detector environment,because, at such a position, the magnetic power of a magnetic fluxgenerator (i.e., the magnets) is changes minimally even when thetemperature of the detector environment is changed (i.e., a temperaturecoefficient of the magnetic flux generator is low at such position).Therefore, in the present disclosure, the position detection accuracy atany position within the movable range of the detection object isimproved irrespective of the temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present disclosure becomemore apparent from the following detailed description made withreference to the accompanying drawings, in which:

FIG. 1 is a sectional view of a position detector and an actuator in afirst embodiment of the present disclosure;

FIG. 2 is a sectional view along line II-II of FIG. 1;

FIGS. 3A, 3B, and 3C are views of a magnetic flux collector in a firstembodiment of the present disclosure;

FIG. 4 is a figure illustrating a relationship between a position of adetection object relative to a reference part and a magnetic fluxdensity that is detected by the magnetic flux density detector, in thefirst embodiment and in a comparative example;

FIG. 5 is a sectional view of the position detector in the comparativeexample;

FIG. 6 is a sectional view of the position detector in a secondembodiment of the present disclosure;

FIG. 7 is a sectional view of the position detector in a thirdembodiment of the present disclosure;

FIG. 8 is a diagram of a relationship between a position of thedetection object relative to the reference part and the magnetic fluxdensity that is detected by the magnetic flux density detector in thethird embodiment of the present disclosure;

FIG. 9 is a sectional view of a position detector in a fourth embodimentof the present disclosure; and

FIG. 10 is a sectional view of a position detector in a fifth embodimentof the present disclosure.

DETAILED DESCRIPTION

Hereafter, the position detector in plural embodiments of the presentdisclosure and the actuator using the same are explained based on thedrawing. In the plural embodiments, the same numerals are assigned tothe same components, and explanation of the same components will not berepeated.

First Embodiment

The position detector in the first embodiment of the present disclosureand the actuator using the same are shown in FIGS. 1 and 2.

An actuator 1 is used as a driving power source which drives a throttlevalve of a vehicle (not illustrated), for example. The actuator 1 isprovided with a motor 2, a housing 5, a cover 6, an electronic controlunit (hereinafter “ECU”) 11, a rotating body 12, a position detector 10,together with other parts.

As shown in FIG. 1, the motor 2 has an output shaft 3, a motor terminal4 and the like. An electric power is supplied to the motor 2 via themotor terminal 4. The motor 2 rotates by receiving the electric powerfrom the terminal 4. Rotation of the motor 2 is outputted from theoutput shaft 3. The output shaft 3 is connected to a throttle valve viaa geartrain (not illustrated) or the like, for example. Therefore, whenthe motor 2 rotates, the throttle valve also rotates.

The housing 5 is made of resin to have a cylinder shape with a bottom,for example, and has the motor 2 accommodated in an inside thereof.

The cover 6 is made of resin to have a cylinder shape with a bottom, forexample, and has its opening abutted to an opening of the housing 5 in astate that the output shaft 3 inserted into a cavity 7 which is bored onthe bottom of the cover 6. In such manner, a hollow space 100 is definedat a position between the cover 6 and the motor 2.

The cover 6 has a connector 8 formed in a pipe shape and extending in aradial outside direction from a cylinder shape body of the cover 6. Inthe connector 8, an end of the motor terminal 4 is exposed. Theconnector 8 is connected to an end of a wire harness leading to the ECU11. Thereby, the electric power from the battery (not illustrated) issupplied to the motor 2 via the ECU 11, the wire harness, and the motorterminal 4.

The ECU 11 is a computer provided with a CPU serving as a calculationunit together with ROM, RAM serving as a memory unit, an input/outputinterface and other parts. The ECU 11 controls the operation of thevarious devices installed in the vehicle based on the signal fromvarious sensors attached to various parts of the vehicle.

The ECU 11 controls the electric power supplied to the motor 2, forexample, based on an accelerator opening signal from an acceleratorpedal, or the like. When the electric power is supplied to the motor 2,the motor 2 rotates to rotate a throttle valve. Therefore, the throttlevalve opens and closes an air intake passage, and an amount of an intakeair flowing through the air intake passage is adjusted. In the presentembodiment, the ECU 11 may also control a supply of the electric powerto the motor 2 by an idle speed control (ISC) function, for example,irrespective of the opening signal from the accelerator pedal.

The rotating body 12 is, for example, made of resin to have a discshape, and is disposed in the hollow space 100. The rotating body 12 isfixed onto the output shaft 3 with the output shaft 3 extendingtherethrough at its center. Therefore, when the output shaft 3 rotates,the rotating body 12 rotates together with the output shaft 3. Since theoutput shaft 3 and the throttle valve are connected by the geartrain,the rotation position of the rotating body 12 corresponds to therotation position of the throttle valve.

According to the present embodiment, the position detector 10 detectsthe rotation position of the rotating body 12 that moves and rotatesrelative to the cover 6. Therefore, by detecting the rotation positionof the rotating body 12 which rotates relative to the cover 6, therotation position of the throttle valve is detected and an openingdegree of the throttle valve is also detected. Thus, the positiondetector 10 is capable of serving as a throttle position sensor.

As shown in FIGS. 1 and 2, the position detector 10 includes a firstmagnetic flux transmission part 20, a second magnetic flux transmissionpart 30, a magnet 45 serving as a first magnetic flux generator, amagnet 50 serving as a second magnetic flux generator, a Hall IC 60serving as a magnetic flux density detector, a first magnetic fluxcollector 70 that concentrates a spill magnetic flux to flow thecollected flux to the Hall IC 60, a second magnetic flux collector 80and the like.

The first magnetic flux transmission part 20 is made of a material whichhas a relatively high magnetic permeability, such as a silicon steel, orthe like. The first magnetic flux transmission part 20 is disposed in anarc-shape cavity 13 that is formed on the rotating body 12.

The first magnetic flux transmission part 20 has a center section 21, afirst end 22, and a second end 23. The center section 21 has a shapewhich extends along a first virtual circle C1 that centers on a rotationaxis O of the rotating body 12 (refer to FIG. 2). The first end 22 isformed to extend from one end of the center section 21 toward a radialoutside of the first virtual circle C1. The second end 23 is formed toextend from the other end of the center section 21 toward the radialoutside of the first virtual circle C1.

The second magnetic flux transmission part 30 is made of the materialwhich has a relatively high magnetic permeability, such as a siliconsteel or the like, similar to the first magnetic flux transmission part20. The second magnetic flux transmission part 30 is disposed in thecavity 13 formed in the rotating body 12.

The second magnetic flux transmission part 30 has a center section 31, afirst end 32, and a second end 33. The center section 31 has a shapewhich extends along a second virtual circle C2 that has a larger radiusthan the first virtual circle C1 and centers on the rotation axis O ofthe rotating body 12 (refer to FIG. 2). The first end 32 is formed toextend from one end of the center section 31 toward a radial inside ofthe second virtual circle C2. The second end 33 is formed to extend fromthe other end of the center section 31 to the radial inside of thesecond virtual circle C2.

In other words, the rotating body 12 rotates relative to the cover 6,and the first magnetic flux transmission part 20 and the second magneticflux transmission part 30 have a curved shape that is concentric to acenter of rotation of the rotating body 12.

As shown in FIGS. 1-4, the first magnetic flux transmission part 20 andthe second magnetic flux transmission part 30 are disposed in the cavity13 of the rotating body 12 so that the center section 21 of the firstmagnetic flux transmission part 20 and the center section 31 of thesecond magnetic flux transmission part 30 face each other in the radialdirection of the first virtual circle C1. Thereby, an arc-shape gap 101is formed between the center section 21 of the first magnetic fluxtransmission part 20 and the center section 31 of the second magneticflux transmission part 30 (refer to FIG. 2).

The magnet 45 is a permanent magnet, such as a neodymium magnet, aferrite magnet, or the like, for example. The magnet 45 has a magneticpole 46 on one end, and has a magnetic pole 47 on the other end. Themagnet 45 is magnetized so that a magnetic pole 46 side serves as an Npole, and a magnetic pole 47 side serves as an S pole. The magnet 45 isdisposed at a position between the first end 22 of the first magneticflux transmission part 20 and the first end 32 of the second magneticflux transmission part 30 so that the magnetic pole 46 abuts the firstend 22 of the first magnetic flux transmission part 20, and the magneticpole 47 abuts the first end 32 of the second magnetic flux transmissionpart 30. Thereby, the magnetic flux generated by the magnetic pole 46 ofthe magnet 45 is transmitted from the first end 22 of the first magneticflux transmission part 20 to the second end 23 via the center section21.

The magnet 50 is also a permanent magnet, such as a neodymium magnet aferrite magnet, or the like, for example, similar to the magnet 45. Themagnet 50 has a magnetic pole 51 on one end, and has a magnetic pole 52on the other end. The magnet 50 is magnetized so that a magnetic pole 51side serves as an N pole, and a magnetic pole 52 side serves as an Spole. The magnet 50 is disposed at a position between the second end 33of the second magnetic flux transmission part 30 and the second end 23of the first magnetic flux transmission part 20 so that the magneticpole 51 abuts the second end 33 of the second magnetic flux transmissionpart 30, and the magnetic pole 52 abuts the second end 23 of the firstmagnetic flux transmission part 20. Thereby, the magnetic flux generatedby the magnetic pole 51 of the magnet 50 is transmitted from the secondend 33 of the second magnetic flux transmission part 30 to the first end32 via the center section 31.

Here, the spill magnetic flux flows through the gap 101, either from thefirst magnetic flux transmission part 20 to the second magnetic fluxtransmission part 30, or from the second magnetic flux transmission part30 to the first magnetic flux transmission part 20.

In the present embodiment, the magnet 45 and the magnet 50 areconfigured to be the same type of permanent magnet (e.g., a neodymiummagnet, a ferrite magnet, etc.), having the same magnet materialcomposition and the same magnetization adjustment method. Regarding andthe same magnetization adjustment method, if the magnets 45, 50 areferrite magnets, for example, the magnets 45, 50 may contain the samepercentage of neodymium, iron, boron and the same percentage compositionof dysprosium, etc. or the percentage composition of barium, strontium,etc. However, the magnet 45 and the magnet 50 differ in volume. In thepresent embodiment, the magnet 45 has a larger volume than the magnet50. Therefore, as shown in FIG. 2, the flow of the spill magnetic fluxat a position P1 that is at a predetermined distance away from thelongitudinal center toward the magnet 50 in the gap 101 is zero, whilethe flow of the same flux flows from the second magnetic fluxtransmission part 30 to the first magnetic flux transmission part 20 inan area between the position P1 and the magnet 50, and the flow of thesame flux flows from the first magnetic flux transmission part 20 to thesecond magnetic flux transmission part 30 in an area between theposition P1 and the magnet 45. More specifically, the closer theposition along the longitudinal direction of the gap 101 is to themagnet 45 or to the magnet 50, the greater an absolute value of themagnetic flux density becomes. Further, the magnetic flux density isequal to 0 at the position P1.

Further, the magnetic flux at positions around the magnet 45 “flies”from the magnetic pole 46 to the magnetic pole 47, and the magnetic fluxat positions around the magnet 50 “flies” from the magnetic pole 51 tothe magnetic pole 52.

As shown in FIG. 2 and FIGS. 3A-3C, the Hall IC 60 has a Hall element 61serving as a signal output element, as well as a sealer 62 and a sensorterminal 63. The Hall element 61 outputs a signal according to thedensity of the magnetic flux passing therethrough. The sealer 62 is madeof resin and has a rectangular board shape, for example. A first end ofthe sensor terminal 63 is connected to the Hall element 61. The sealer62 covers an entire Hall element 61, as well as the first end of thesensor terminal 63. In this case, the Hall element 61 is located at thecenter of the sealer 62.

The sealer 62 sealing the Hall IC 60 and the first end of the sensorterminal 63 is molded by a mold 9. The mold 9 is a resin mold, forexample, and has a square pole shape. The sealer 62 sealing the Hall IC60 is molded at a position on one end side of the mold 9.

The mold 9 is disposed on the cover 6 so that one end of the mold 9 ispositioned in the gap 101 and the other end of the mold 9 is connectedto the bottom of the cover 6. In such manner, the Hall IC 60 isrotatably moved, relative to the rotating body 12, in the gap 101between the first magnetic flux transmission part 20 and the secondmagnetic flux transmission part 30. The cover 6 and the mold 9 arerespectively equivalent to a reference part in the claims, and therotating body 12 is equivalent to a detection object in the claims.

The sensor terminal 63 of the Hall IC 60 has a second end formed to beexposed in an inside of the connector 8 of the cover 6 by aninsert-molding method in the cover 6. Therefore, when an end of the wireharness leading to the ECU 11 is connected to the connector 8, the Hallelement 61 of the Hall IC 60 is connected to the ECU 11. Thereby, asignal from the Hall element 61 is transmitted to the ECU 11.

In this case, the magnetic flux passing through the Hall element 61 ofthe Hall IC 60 is mainly made of the spill magnetic flux which flowsthrough the gap 101 between the first magnetic flux transmission part 20and the second magnetic flux transmission part 30 either (i) from thesecond magnetic flux transmission part 30 to the first magnetic fluxtransmission part 20 or (ii) from the first magnetic flux transmissionpart 20 to the second magnetic flux transmission part 30.

In the present embodiment, the spill magnetic flux flows from the firstmagnetic flux transmission part 20 to the second magnetic fluxtransmission part 30 in an area between the position P1, that isshifted-toward-magnet 50, and the magnet 45 as mentioned above. Thespill magnetic flux flows from the second magnetic flux transmissionpart 30 to the first magnetic flux transmission part 20 in an areabetween the position P1 and the magnet 50. Further, when a positionalong the longitudinal direction of the gap 101 is closer to the magnet45 or to the magnet 50, the greater an absolute value of the magneticflux density becomes.

Therefore, if assumed that a flow direction of the spill magnetic fluxflowing from the second magnetic flux transmission part 30 to the firstmagnetic flux transmission part 20 is a negative direction, when aposition of the Hall IC 60 rotatably moves from a proximity of themagnet 50 to a proximity of the magnet 45 in the gap 101, the magneticflux density monotonically increases from a negative value to a positivevalue, thereby identifying a rotation position of the Hall IC 60uniquely according to the detected magnetic flux density and thusoutputting a signal that uniquely identifies the rotation position ofthe Hall IC 60.

According to the above-mentioned configuration, the ECU 11 is capable ofdetecting the rotation position of the rotating body 12 relative to thecover 6 based on the signal outputted from the Hall IC 60. In suchmanner, the rotation position and an opening degree of the throttlevalve are detected.

The first magnetic flux collector 70 is made of a relatively highmagnetically permeable material such as a permalloy or the like, and hasa hexahedron body. The first magnetic flux collector 70 is disposed on afirst side of the mold 9 so that a predetermined face 71 of thecollector 70 faces or abuts a center of one face on a first magneticflux transmission part 20 side of the sealer 62 of the Hall IC 60. Anopposite face 72 of the first magnetic flux collector 70, which isopposite to the face 71, faces the center section 21 of the firstmagnetic flux transmission part 20.

The second magnetic flux collector 80 is, similar to the first magneticflux collector 70, made of a relatively high magnetically permeablematerial such as a permalloy or the like, and has a hexahedron body. Thesecond magnetic flux collector 80 is disposed on a second side of themold 9 so that a predetermined face 81 of the collector 80 faces orabuts a center of one face on a second magnetic flux transmission part30 side of the sealer 62 of the Hall IC 60. A face 82 of the secondmagnetic flux collector 80, which is opposite to the face 81, faces thecenter section 31 of the second magnetic flux transmission part 30.

Thus, the Hall IC 60 is sandwiched or bound in between the firstmagnetic flux collector 70 and the second magnetic flux collector 80,and such sandwiching or binding direction is substantially the same asthe facing direction between the first magnetic flux transmission part20 and the second magnetic flux transmission part 30. The spill magneticflux which flows through the gap 101 between the first magnetic fluxtransmission part 20 and the second magnetic flux transmission part 30is thus concentrated in such manner, and is directed to flow to (i.e.,pass through) the Hall IC 60.

In the present embodiment, the minimum (i.e., zero in this embodiment)magnetic flux (MF) density position where an absolute value of themagnetic flux density is observed as 0 is changed/adjusted to anyposition (i.e., at the position P1 in this embodiment) between themagnet 45 and the magnet 50 along the longitudinal direction of relativemovement of the Hall IC 60 in the gap 101 (i.e., along a path ofrelative movement direction of the IC 60), by an adjustment of thevolume difference between the magnet 45 and the magnet 50, for example.In other words, the minimum MF density position may be moved and set toany position within the movable range of the rotating body 12 in thepresent embodiment, which may be a position other than the centerposition of the movable range.

Generally, at the minimum MF density position within the movable rangeof the Hall IC 60, where an absolute value of the magnetic flux densityis observed as the minimum, the magnetic power of the magnet 45 and themagnet 50 changes minimally according to the temperature coefficient ofthose magnets. That is, the tolerance for the temperature change isimproved at such position. Therefore, at the proximity of the minimum MFdensity position within the movable range of the Hall IC 60, theposition detection accuracy of the position detector 10 is high.

According to the present embodiment, when the throttle valve is in afully-closed state, the Hall IC 60 is located at a position closest tothe magnet 50 in the movable range in the gap 101 (i.e., at the positionP1). On the other hand, when the throttle valve is a fully-opened state,the Hall IC 60 is located at a position closest to the magnet 45 in themovable range in the gap 101.

The throttle valve position is required to have the highest positiondetection accuracy at or around a fully-closed position. As mentionedabove, in the present embodiment, the minimum MF density position may bemoved and set to any position within the movable range of the rotatingbody 12. Therefore, in the present embodiment, the minimum MF densityposition may be moved and set to a rotation position of the rotatingbody 12 which corresponds to the fully-closed position of the throttlevalve. Therefore, the position detection accuracy at or around thefully-closed position of the throttle valve is improved irrespective ofthe temperature.

According to the present embodiment, the magnetic flux density detectedby the Hall IC 60 is illustrated by a line L1 in FIG. 4. In addition tothe spill magnetic flux which flows between the first magnetic fluxtransmission part 20 and the second magnetic flux transmission part 30,the magnetic flux which “flies” from the magnetic pole 46 to themagnetic pole 47 of the magnet 45 and the magnetic flux which “flies”from the magnetic pole 51 to the magnetic pole 52 of the magnet 50 flowat or around the magnets 45 and 50 in the gap 101. Therefore, a changerate of the absolute value illustrated by the line L1 increases towardboth ends of the line L1.

In the present embodiment, the relationship between the magnetic fluxdensity and a position of the rotating body 12 in the movable range(i.e., a range between the fully-closed position and the fully-openedposition of the throttle valve) is shown in FIG. 4. Thus, in the presentembodiment, the position of the rotating body 12 is detected in a rangein which the linearity of the line L1 is relatively high.

The advantageous points of the position detector in the presentembodiment are clarified by describing a comparative example of aposition detector in the following.

As shown in FIG. 5, in the comparative example, the magnet 45 in thefirst embodiment is replaced with a magnet 40.

The magnet 40 is a permanent magnet, such as a neodymium magnet, aferrite magnet, or the like, for example, which has a magnetic pole 41on one end and a magnetic pole 42 on the other end. The magnet 40 ismagnetized to have the magnetic pole 41 serving as an N pole and themagnetic pole 42 serving as an S pole. The magnet 40 is disposed so thatthe magnetic pole 41 abuts the first end 22 of the first magnetic fluxtransmission part 20 and the magnetic pole 42 abuts the first end 32 ofthe second magnetic flux transmission part 30. Thereby, the magneticflux generated by the magnetic pole 41 of the magnet 40 is transmittedfrom one end to the other end of the first magnetic flux transmissionpart 20.

Here, the spill magnetic flux flows through the gap 101 either (i) fromthe first magnetic flux transmission part 20 to the second magnetic fluxtransmission part 30 or (ii) from the second magnetic flux transmissionpart 30 to the first magnetic flux transmission part 20.

In the comparative example, the magnet 40 and the magnet 50 arerespectively configured to be permanent magnets having the same volume,the same magnet type (e.g., a neodymium magnet, a ferrite magnet, etc.),the same material composition (e.g., the same rate of neodymium, iron,boron plus the same content rate of dysprosium etc. if the magnets 40,50 are neodymium magnets; or the same contents rate of barium,strontium, etc. if the magnets 40, 50 are ferrite magnets), and the samemagnetization adjustment method. Therefore, the flow of the spillmagnetic flux at the longitudinal center of the gap 101 is zero, whilethe flow of the same flux flows from the second magnetic fluxtransmission part 30 to the first magnetic flux transmission part 20 inan area between the center of the gap 101 and the magnet 50 and the flowof the same flux flows from the first magnetic flux transmission part 20to the second magnetic flux transmission part 30 in an area between thecenter of the gap 101 and the magnet 45. More specifically, the closerthe position along the longitudinal direction of the gap 101 is to themagnet 45 or to the magnet 50, the greater an absolute value of themagnetic flux density becomes. Further, the magnetic flux density isequal to 0 at the longitudinal center of the gap 101.

Further, the magnetic flux at positions around the magnet 40 “flies”from the magnetic pole 41 to the magnetic pole 42, and the magnetic fluxat positions around the magnet 50 “flies” from the magnetic pole 51 tothe magnetic pole 52.

In the comparative example, the magnetic flux density detected by theHall IC 60 is illustrated by a line L2 in FIG. 4, which is adashed-dotted line. As such, the minimum MF density position in thecomparative example is fixedly set at the center (i.e., position 0 inFIG. 4) of the movable range of the rotating body 12. Therefore, if theposition detector in the comparative example is used to detect aposition (i.e., an opening degree) of the throttle valve, the positiondetection accuracy at or around the fully-closed position of thethrottle valve may be deteriorated.

On the other hand, in the present embodiment, the minimum MF densityposition is set at a rotation position of the rotating body 12corresponding to the fully-closed position of the throttle valve.Therefore, the position detection accuracy at or around the fully-closedposition is improved. Thus, the position detector in the presentembodiment is capable of more suitably detecting a position (i.e., anopening degree) of the throttle valve in comparison to the detector inthe comparative example.

As explained above, in the present embodiment, the minimum MF densityposition, where the absolute value of the magnetic flux density isobserved as the minimum (i.e., zero in the present embodiment), is setat the position P1 that is shifted by a predetermined distance away fromthe longitudinal center toward the magnet 50 in the gap 101 (i.e., theshift of the position P1 from the longitudinal center along a directionof relative movement direction of the Hall IC 60 in the gap 101 betweenthe first magnetic flux transmission part 20 and the second magneticflux transmission part 30). That is, in the present embodiment, theminimum MF density position can be moved and set at any position otherthan the center of the movable range of the rotating body 12. Therefore,when the position detector 10 of the present embodiment is applied tothe rotating body 12 (i.e., a throttle valve), such a position detector10 is capable of moving the minimum MF density position to a desiredposition having the highest position detection accuracy.

Generally, at the minimum MF density position within the movable rangeof the Hall IC 60, the magnetic power of the magnet 45 and the magnet 50is changes minimally according to the temperature coefficient of thosemagnets. That is, the tolerance for the temperature change is improvedat such position. Therefore, in the present embodiment, the positiondetection accuracy is improved for any position within the movable rangeof the rotating body 12 (i.e., the throttle valve) irrespectively of thetemperature.

In the present embodiment, the magnet 45 is a permanent magnet and themagnet 50 is provided as, relative to the magnet 45, a permanent magnethaving at least one different attribute from among the volume, the type,the material composition, and the magnetization adjustment method. Inother words, at least one of a magnet volume, a magnet type, a magnetmaterial composition, or a magnetization adjustment method of the magnet45 is different from the magnet 50. That is, in the present embodiment,the volume of the magnet 50 is different from the magnet 45. Thereby,the minimum MF density position may be moved and set at any positionother than the center of the movable range of the rotating body 12.

Second Embodiment

The position detector in the second embodiment of the present disclosureis shown in FIG. 6. In the second embodiment, the first magnetic fluxgenerator is different from the first embodiment.

According to the second embodiment, the first magnetic flux generatorhas two pieces of the magnets 40. The magnet 40 is a magnet shown in theabove-mentioned comparative example. That is, the magnet 40 and themagnet 50 are respectively configured to be permanents magnet having thesame magnet volume, the same magnet type (e.g., a neodymium magnet, aferrite magnet, etc.), the same material composition (e.g., the samerate of neodymium, iron, boron plus the same content rate of dysprosiumetc. if the magnets 40, 50 are neodymium magnets; or the same contentsrate of barium, strontium, etc. if the magnets 40, 50 are ferritemagnets), and the same magnetization adjustment method.

As shown in FIG. 6, two magnets 40 are arranged in parallel at aposition between (i) the first end 22 of the first magnetic fluxtransmission part 20 and (ii) the first end 32 of the second magneticflux transmission part 30 in the present embodiment. Here, the magneticpole 41 of the two magnets 40 abuts the first end 22, and the magneticpole 42 of the two magnets 40 abuts the first end 32.

By devising the above-mentioned configuration, the flow of the spillmagnetic flux at a position P2, that is at a predetermined distance awayfrom the longitudinal center toward the magnet 50 in the gap 101, iszero, while (i) the flow of the same flux flows from the second magneticflux transmission part 30 to the first magnetic flux transmission part20 in an area between the position P2 and the magnet 50 and (ii) theflow of the same flux flows from the first magnetic flux transmissionpart 20 to the second magnetic flux transmission part 30 in an areabetween the position P2 and the magnet 40. More specifically, the closerthe position along the longitudinal direction of the gap 101 is to themagnet 40 or to the magnet 50, the greater an absolute value of themagnetic flux density becomes. Further, the magnetic flux density isequal to 0 at the position P2.

As explained above, in the present embodiment, the first magnetic fluxgenerator has two permanent magnets (i.e., dual magnets 40) and thesecond magnetic flux generator has different number of the samepermanent magnets (i.e., a single magnet 50 in this embodiment). Thatis, the same permanent magnet of the same volume, same type, samematerial composition, and same magnetization adjustment method isprovided in different number of pieces on the right and left sides ofthe two magnetic transmission parts. In other words, the first magneticflux generator has at least one permanent magnet, the second magneticflux generator has a different number of permanent magnets as the firstmagnetic flux generator, and identical permanent magnets are used forthe magnets 40 and the magnet 50.

Therefore, in the present embodiment, the minimum MF density positioncan be moved and set at any position other than the center of themovable range of the rotating body 12, similar to the first embodiment.Thus, the minimum MF density position can be moved and set to therotation position of the rotating body 12, which corresponds to thefully-closed position of the throttle valve. As a result, the positiondetection accuracy at the proximity of the fully-closed position of thethrottle valve is improved irrespective of the temperature.

Further, in the present embodiment, the first magnetic flux generatorand the second magnetic flux generator are configured to have one or twosame (i.e., standard) permanent magnets having the same attributes(i.e., volume/type/material composition/magnetization adjustmentmethod). Therefore, the manufacturing cost for manufacturing differentmagnets having different attributes will be saved by using such standardmagnet. Also, efficiencies from manufacturing such standard magnet involume may be realized.

Third Embodiment

The position detector in the third embodiment of the present disclosureis shown in FIG. 7. According to the third embodiment, the positiondetector 10 has a third magnetic flux transmission part 53. The thirdmagnetic flux transmission part 53 is disposed at a position between thesecond end 23 of the first magnetic flux transmission part 20 and thesecond end 33 of the second magnetic flux transmission part 30, and ismade of the same material as the first magnetic flux transmission part20 and the second magnetic flux transmission part 30, to be integratedto the first magnetic flux transmission part 20 and to the secondmagnetic flux transmission part 30. That is, in other words, theconfiguration of the position detector 10 in the third embodiment may bedescribed as a replacement of the magnet 50 of the above-mentionedcomparative example with the third magnetic flux transmission part 53.

According to the present embodiment, in an entire range of thelongitudinal direction of the gap 101, the spill magnetic flux flowsfrom the center section 21 of the first magnetic flux transmission part20 to the center section 31 of the second magnetic flux transmissionpart 30. In such configuration, the closer the position in the gap 101along the longitudinal direction is to the magnet 40, the greater theabsolute value of the magnetic flux density becomes. Further, a positionP4 that is shifted by a predetermined distance shifted away from thelongitudinal center of the gap 101 (refer to FIG. 7) corresponds to thefully-closed position of the throttle valve.

By devising the above-mentioned configuration, the magnetic flux densitydetected by the Hall IC 60 is illustrated by a line L3 in FIG. 8. Thatis, a relationship between the magnetic flux density and the position ofthe rotating body 12 in the movable range of the rotating body 12 (i.e.,a range between the fully-closed position and the fully-opened positionof the throttle valve) is illustrated in FIG. 8.

According to the present embodiment, the position P4 corresponds to theminimum MF density position (i.e., a non-zero minimum value in thiscase) within the range of relative movement of the Hall IC 60 (i.e., therange between the fully-closed position and the fully-opened position ofthe throttle valve). Therefore, the position detection accuracy at theproximity of the fully-closed position of the throttle valve is improvedirrespective of the temperature.

Further, in the present embodiment, the manufacturing cost of theposition detector 10 is reduced, since the detector 10 uses fewerpermanent magnets in comparison to the above-mentioned embodiment.

Fourth Embodiment

The position detector in the fourth embodiment of the present disclosureis shown in FIG. 9. According to the fourth embodiment, the width orthickness (‘t’ in FIG. 9) of both of the center sections 21, 31 of thefirst and second magnetic flux transmission parts 20, 30, respectively,which is measured perpendicularly at positions along the longitudinaldirection of both of the center section 21 and the center section 31, isthinner as the width measurement position approaches the magnet 50 fromthe magnet 40. In other words, the thickness of at least one of thefirst magnetic flux transmission part 20 or the second magnetic fluxtransmission part 30 changes in a direction from the magnet 40 to themagnet 50.

In the above-mentioned configuration, as shown in FIG. 9, the flow ofthe spill magnetic flux at a position P5 that is shifted by apredetermined distance away from the longitudinal center toward themagnet 50 in the gap 101 is zero, while (i) the flow of the same fluxflows from the second magnetic flux transmission part 30 to the firstmagnetic flux transmission part 20 in an area between the position P5and the magnet 50 and (ii) the flow of the same flux flows from thefirst magnetic flux transmission part 20 to the second magnetic fluxtransmission part 30 in an area between the position P5 and the magnet40. Further, the magnetic flux density is equal to 0 at the position P5.

According to the present embodiment, the minimum MF density position isset to the rotation position of the rotating body 12 which correspondsto the fully-closed position of the throttle valve, similar to the firstembodiment. Therefore, the position detection accuracy at the proximityof the fully-closed position of the throttle valve is improvedirrespective of the temperature.

Further, in the present embodiment, the first magnetic flux generatorand the second magnetic flux generator are configured to have one or twosame (i.e., standard) permanent magnets having the same attributes(i.e., volume/type/material composition/magnetization adjustmentmethod). Therefore, the manufacturing cost for manufacturing differentmagnets having different attributes will be saved by using such standardmagnet. Also, efficiencies from manufacturing such standard magnet involume may be realized.

Fifth Embodiment

The position detector in the fifth embodiment of the present disclosureis shown in FIG. 10. In the fifth embodiment, the shape of the firstmagnetic flux transmission part and the second magnetic fluxtransmission part is different from the first embodiment together withother attributes.

According to the fifth embodiment, a mover 110 serving as a detectionobject is attached to a manual valve which switches a shift of a gearboxof a vehicle, for example. The manual valve moves linearly in an axialdirection, for switching the shift of the gearbox. The mold 9 is fixedonto a separate member that is close to but separate from the manualvalve. That is, the mover 110 moves linearly relative to the mold 9 thatserves as a reference part.

According to the present embodiment, the position detector detects theposition of the mover 110 that moves linearly relative to the mold 9.Thereby, the position of the manual valve is detected and an actualshift position of the gearbox is detected. Thus, the position detectorcan be used as a stroke sensor (i.e., a linear movement sensor).

As shown in FIG. 10, in the present embodiment, a first magnetic fluxtransmission part 24 is disposed in a cavity 111 having a rectangularshape that is bored in the mover 110. The first magnetic fluxtransmission part 24 has a center section 25, a first end 26, and asecond end 27. The center section 25 has a straight shape which isparallel to a virtual straight line S extending in a direction of therelative movement of the mover 110. The first end 26 extendssubstantially perpendicular from one end of the center section 25relative to the virtual straight line S. The second end 27 extends fromthe other end of the center section 25 in the same direction as thefirst end 26.

A second magnetic flux transmission part 34 is also disposed in thecavity 111 of the mover 110. The second magnetic flux transmission part34 has a center section 35, a first end 36, and an second end 37. Thecenter section 35 has a straight shape which is in parallel with thevirtual straight line S similar to the center section 25. The first end36 extends substantially perpendicularly from one end of the centersection 35 relative to the virtual straight line S, to face the firstend 26. The second end 37 extends from the other end of the centersection 35 in the same direction as the first end 36.

In other words, the mover 110 moves linearly relative to the referencepart 9, and the first magnetic flux transmission part 24 and the secondmagnetic flux transmission part 34 have a straight shape that extendsalong a path of relative movement of the mover 110.

As shown in FIG. 10, the first magnetic flux transmission part 24 andthe second magnetic flux transmission part 34 are formed in the cavity111 of the mover 110 so that the center section 25 and the centersection 35 face each other in a direction that is perpendicular to thevirtual straight line S. Thereby, a rectangular shape gap 102 is definedbetween the center section 25 of the first magnetic flux transmissionpart 24 and the center section 35 of the second magnetic fluxtransmission part 34.

The configuration of the fifth embodiment is similar to the firstembodiment, other than the above-described points.

According to the present embodiment, the magnetic flux density detectedby the Hall IC 60 is substantially illustrated as a line L1 shown inFIG. 4, if “a rotation position (θ)” of FIG. 4 is read as a “position”in a path of relative movement direction of the mover 110.

In the present embodiment and similar to the first embodiment, thevolume of the magnet 45 is different from the volume of the magnet 50.Thereby, the minimum MF density position is set at any position otherthan the longitudinal center of the movable range of the mover 110.Therefore, when the position detector of the present embodiment isapplied to the mover 110 (i.e., a manual valve) which is required tohave the highest position detection accuracy at any position other thanthe center of the movable range, the minimum MF density position may bepositioned where the position detection accuracy is required to behighest.

Other Embodiments

In the above-mentioned first embodiment, the magnet serving as the firstmagnetic flux generator and the magnet serving as the second magneticflux generator are respectively different from each other in theirvolumes. On the other hand, in other embodiments of the presentdisclosure, the magnet serving as the second magnetic flux generator maybe provided as a permanent magnet having at least one differentattribute from the magnet serving as the first magnetic flux generator,from among the following attributes of the volume, the type, thematerial composition, and the magnetization adjustment method. In suchmanner, the minimum MF density position may be moved and set at anyposition other than the center of the movable range of the detectionobject.

In the second embodiment mentioned above, an example of having the samestandard magnet in different numbers for the first and second magneticflux generator is described. That is, in the second embodiment, thefirst magnetic flux generator has only one standard magnet, while thesecond magnetic flux generator has two standard magnets, which have thesame volume/type/material composition/magnetization adjustment method.On the other hand, in other embodiments of the present disclosure, aslong as the number of such standard magnets differs between the firstmagnetic flux generator and the second magnetic flux generator, thenumber of the permanent magnets (i.e., the standard magnets) may bearbitrarily determined.

In the third embodiment described above, the second magnetic fluxgenerator is replaced with the third magnetic flux transmission partmade of the same material as the first magnetic flux transmission partand the second magnetic flux transmission part. On the other hand, inother embodiments of the present disclosure, the first magnetic fluxgenerator, instead of the second magnetic flux generator, may bereplaced with the third magnetic flux transmission part.

In the fourth embodiment described above, the widths of the firstmagnetic flux transmission part and the second magnetic fluxtransmission part are respectively thinned toward the second magneticflux generator. On the other hand, in other embodiments of the presentdisclosure, the first magnetic flux transmission part and the secondmagnetic flux transmission part may be formed to have a greater widthtoward the second magnetic flux generator. Further, the width of onlyone of the first and second magnetic flux transmission parts, may bethinned or widened toward the second magnetic flux generator.

In the above-mentioned embodiment, it is described that the firstmagnetic flux transmission part, the second magnetic flux transmissionpart, the first magnetic flux generator, and the second magnetic fluxgenerator are disposed on the detection object, and the magnetic fluxdensity detector is disposed on the reference part. On the other hand,in other embodiments of the present disclosure, the first magnetic fluxtransmission part, the second magnetic flux transmission part, the firstmagnetic flux generator, and the second magnetic flux generator may bedisposed on the reference part, and the magnetic flux density detectormay be disposed on the detection object.

In other embodiments of the present disclosure, the polarity of themagnet disposed at a position between the both ends of the firstmagnetic flux transmission part and the second magnetic fluxtransmission part may be flipped or reversed from the positionsreflected in the above-described embodiments.

Further, in other embodiments of the present disclosure, the motor mayhave a speed reducer for reducing the number of rotations to betransmitted to the output shaft.

Additionally, in other embodiments of the present disclosure, each ofthe above-mentioned embodiments may be combined with other embodiments.

Moreover, in other embodiments of the present disclosure, an actuatormay be used, for example, as a driving power source of various devices,such as a wastegate valve operation device, a variable vane controldevice of a variable capacity turbocharger, a valve operation device ofan exhaust throttle or an exhaust switch valve, a valve operation deviceof a variable air intake mechanism, and the like.

Although the present disclosure has been fully described in connectionwith the above embodiment thereof with reference to the accompanyingdrawings, it is to be noted that various changes and modifications willbecome apparent to those skilled in the art, and such changes andmodifications are to be understood as being within the scope of thepresent disclosure as defined by the appended claims.

What is claimed is:
 1. A position detector configured to detect aposition of a detection object that moves relative to a reference part,the position detector comprising: a first magnetic flux transmissionpart disposed on one of the detection object or the reference part, thefirst magnetic flux transmission part having a first end and a secondend; a second magnetic flux transmission part disposed to define a gapbetween the first magnetic flux transmission part and the secondmagnetic flux transmission part, the second magnetic flux transmissionpart having a first end and a second end; a first magnetic fluxgenerator positioned between the first end of the first magnetic fluxtransmission part and the first end of the second magnetic fluxtransmission part; a second magnetic flux generator positioned betweenthe second end of the first magnetic flux transmission part and thesecond end of the second magnetic flux transmission part; and a magneticflux density detector disposed on another of the detection object or thereference part to be movable within the gap relative to the one of thedetection object or the reference part and configured to output a signalaccording to a density of a magnetic flux passing through the magneticflux density detector, wherein a minimum magnetic flux density positionof the magnetic flux density detector within the gap, where an absolutevalue of the density of the magnetic flux passing through the magneticflux density detector decreases to a minimum, is set to a position thatis shifted away from a center of the gap by a predetermined distancetoward one of the first magnetic flux generator or the second magneticflux generator, and wherein both the first magnetic flux generator andthe second magnetic flux generator have at least one permanent magnetand at least one of the first magnetic flux generator and the secondmagnetic flux generator has more than one permanent magnet.
 2. Theposition detector of claim 1, wherein at least one of a magnet volume, amagnet type, and a magnetic material composition of the at least onepermanent magnet of the first magnetic flux generator is different thanthe at least one permanent magnet of the second magnetic flux generator.3. The position detector of claim 1, wherein the permanent magnets inthe first magnetic flux generator and the second magnetic flux generatorare identical.
 4. The position detector of claim 1 further comprising athird magnetic flux transmission part, wherein the third magnetic fluxtransmission part is made of an identical material as the first magneticflux transmission part and the second magnetic flux transmission part,and wherein the third magnetic flux transmission part replaces the oneof the first magnetic flux generator or the second magnetic fluxgenerator having a lesser number of permanent magnets.
 5. The positiondetector of claim 1, wherein a thickness of at least one of the firstmagnetic flux transmission part or the second magnetic flux transmissionpart changes in a direction from the first magnetic flux generator tothe second magnetic flux generator.
 6. The position detector of claim 1,wherein the detection object rotates relative to the reference part, andthe first magnetic flux transmission part and the second magnetic fluxtransmission part have a curve shape that is concentric to a center ofrotation of the detection object.
 7. The position detector of claim 1,wherein the detection object moves linearly relative to the referencepart, and the first magnetic flux transmission part has a straight shapethat extends along a path of relative movement of the detection object.8. The position detector of claim 1, wherein the first magnetic fluxgenerator has multiple permanent magnets and the second magnetic fluxgenerator has one permanent magnet, and wherein the permanent magnets ofthe first magnetic flux generator are oriented polarity-wise in a samedirection, such that a like pole of each of the permanent magnets in thefirst magnetic flux generator is oriented toward the first magnetic fluxtransmission part, and such that the like pole of the permanent magnetin the second magnetic flux generator is oriented toward the secondmagnetic flux transmission part.
 9. The position detector of claim 8,wherein the like pole is a north pole.
 10. The position detector ofclaim 1, wherein the first magnetic flux generator has multiplepermanent magnets and the second magnetic flux generator has multiplepermanent magnets, and wherein the first magnetic flux generator hasmore permanent magnets than the second magnetic flux generator.
 11. Aposition detector detecting a position of a detection object that movesrelative to a reference part, the position detector comprising: a firstmagnetic flux transmission part disposed on one of the detection objector the reference part, the first magnetic flux transmission part havinga first end and a second end; a second magnetic flux transmission partdisposed to define a gap between the first magnetic flux transmissionpart and the second magnetic flux transmission part, the second magneticflux transmission part having a first end and a second end; a magneticflux generator positioned between the first end of the first magneticflux transmission part and the first end of the second magnetictransmission part, the magnetic flux generator including two or morepermanent magnets; a magnetic flux density detector disposed on anotherof the detection object or the reference part and configured to moverelative to the one of the detection object or the reference part withinthe gap, the magnetic flux density detector further configured to outputa signal based on a magnetic flux density passing through the magneticflux density detector, wherein a minimum magnetic flux density positionof the magnetic flux density detector within the gap, where an absolutevalue of the magnetic flux density passing through the magnetic fluxdensity detector decreases to a minimum, is set to a position that isshifted away from a center of the gap by a predetermined distance awayfrom the magnetic flux generator.